Re: Effects of cascading references in foreign keys

On Oct 29, 2005, at 9:48 AM, Bruno Wolff III wrote:

> On Sat, Oct 29, 2005 at 13:10:31 +0200,
>   Martin Lesser <ml-pgsql@bettercom.de> wrote:
>
>> Which effects have UPDATEs on REFERENCEd TABLEs when only columns
>> in the
>> referenced table are updated which are not part of the FOREIGN KEY
>> constraint?
>
> In 8.1 there is a check to see if the foreign key value has changed
> and if
> not a trigger isn't queued. In the currently released versions any
> update
> will fire triggers.
> The check in comment for trigger.c didn't say if this optimization
> applied
> to both referencing and referenced keys or just one of those.
> If you need to know more you can look at the code at:
> http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/
> for trigger.c.

It seems like this warrants an item somewhere in the release notes,
and I'm not currently seeing it (or a related item) anywhere. Perhaps
E.1.3.1 (Performance Improvements)? For some of the more extreme
UPDATE scenarios I've seen, this could be a big win.

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Thomas F. O'Connell
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